Deep-sky tour
We search for galaxies at the bottom of the Bowl of Virgo
1 NGC 4753
This month’s objects are galaxies located close to the bottom of the Bowl of Virgo. This is a giant semi-circular asterism in Virgo, the bottom of which is marked by mag. +2.7 Porrima (Gamma (g) Virginis). Starting at Porrima, heading east by 2.8˚ will bring you to the lenticular (shaped like an eye lens) galaxy NGC 4753. At mag. +9.9 this is an easy target for a 150mm scope, appearing as a 2 x 1.5 arcminute elliptical glow with a star-like nucleus. A 250mm scope shows a similar view with a hint of a dark feature cutting across the northeast edge. A member of the Virgo II Galaxy Group, it’s around 60.5 million lightyears away. SEEN IT
2 NGC 4666
We move closer to the edge of the Bowl asterism for a highly inclined spiral galaxy known as NGC 4666. Shining with an integrated magnitude of +10.8, NGC 4666 lies 1.3˚ northeast of Porrima and is visible in a 150mm scope. Its almost edge-on nature presents an object which appears around 3 arcminutes-long but just 0.5 arcminutes wide; a glowing streak. A 250mm scope will reveal the core region as a thin bright elongated feature within the larger halo. The extremities of this galaxy, the thin ends of the outer halo furthest from the core, are indistinct. It’s around 80 million lightyears away. SEEN IT
3 NGC 4517
Spiral galaxy NGC 4517 lies within the Bowl asterism and exemplifies the difficulties navigating this part of the sky because, although the Bowl contains many galaxies, there are few stars which can be used to navigate to them. For NGC 4517, head west from Porrima for 1.8˚ to locate mag. +7.1 HIP 61358. Head north for 1.1˚ and west a further 0.3˚ to reach mag. +8.3 HIP 61240. NGC 4517, also known as Reinmuth 80, lies 0.4˚ and a fraction west of this star. It’s a mag. +10.4 object with low surface brightness. A 150mm scope will just about show it. A 250mm instrument fares little better but does manage to reveal its elongated nature. NGC 4517 is 40 million lightyears distant. SEEN IT
4 NGC 4536
We move further into the Bowl of Virgo for an intermediate spiral known as NGC 4536. This has a magnitude of +10.4 but low surface brightness, which makes it faint in smaller scopes. A 250mm scope shows its elongated outline well, the galaxy appearing stretched into a 6 x 2 arcminute ellipse. Locating this galaxy takes even more hunting skill than NGC 4517.
Start at Porrima and head 0.9˚ northwest to locate mag. +7.2 HIP 61711. Nudge your scope 0.1˚ west, then head north for 2.7˚ to locate mag. +5.7 HIP 61658. This forms the eastern corner of the rectangular asterism marked on our chart from which you should be able to find NGC 4536.
It’s around 49 million lightyears away. SEEN IT
5 NGC 4527
At the same magnitude of +10.4 as NGC 4536, our next target, another intermediate galaxy called NGC 4527, is easier to see. Visible in a 150mm scope, it appears as an elongated elliptical glow 3x0.7 arcminutes in size. If you managed to locate target 4, NGC 4536, locating NGC 4527 will be a breeze because it’s located just 28 arcminutes further north. A 250mm instrument shows the galaxy nicely, its outline appearing distinct against the surrounding space. Photos show NGC 4527 to look similar in appearance and inclination to the Andromeda Galaxy. NGC 4527 is estimated to be 49 million lightyears away. SEEN IT
6 NGC 4636
NGC 4636 is an elliptical galaxy which is 53 million lightyears from Earth. It requires a bit of navigational skill to locate manually, forming the eastern point of an equilateral triangle, with mag. +5.7 HIP 61658 and mag. +6.3 HIP 61637 as the western ‘base’. Fortunately, NGC 4636 is a bit easier to identify, being listed at mag. +9.6 and with a diameter around 1.5 arcminutes. It stands out in a 150mm scope, a fuzzy glow with a faint star-like nucleus. A larger instrument shows a similar, albeit brighter, view. Larger apertures help to emphasise how the inner halo brightens towards the stellar core. SEEN IT